I. Field of the Invention
This invention concerns a circulating gas oven, cyclable from heating to cooling modes. It is particularly useful for testing the foaming of liquids at elevated temperatures.
II. Description of Arts, Problems, and Needs, Including Information Disclosed Per 37 CFR 1.56, 1.97 & 1.99
As set forth in Selby et al., U.S. patent application Ser. No. 08/782,822 filed on Jan. 13, 1997, now U.S. Pat. No. 5,824,886, one of the problems with liquids, including lubricants, is foam which can form under operating conditions. In order to test this, and in the process determine a standard property of such liquids, techniques such as the ASTM-D-892 test method have been used for some time. In the ASTM-D-892 test method, foaming characteristics of lubricating oils are determined at temperatures up to ninety-three and one half degrees Celsius. An air bubbling stone is set in the sample; the sample is heated appropriately as air is bubbled in, and foam characteristics of the sample are observed over a period of time. However, with the advent of modern engines, the oils and other lubricants which are employed in the engines are made subject to higher and higher operating temperatures. Thus, it becomes desirable to test for the characteristics of such fluids at or above such temperatures, and among such desired tests is a high temperature foaming test, up to and above one hundred fifty degrees Celsius. However that may be, currently available liquid-filled baths to test for and monitor foam characteristics, and in particular as might be encountered at high temperatures, have several drawbacks. Among these are included the following:
1) A lack of an ability to heat and cool quickly.
2) A lack of ability to see through the bath liquid.
3) Requirement of more than one bath.
4) Requirement of frequent bath liquid changes.
5) Difficulty of handling sample containers coming from the liquid bath and coated with hot oil--plus hot cabinetry.
6) Difficulty of operation.
In addressing such matters, the aforementioned Selby et al. application, which incorporated and claimed the benefit of U.S. provisional patent application Serial Nos. 60/012,576 filed on Feb. 29, 1996 and 60/026,429 filed on Sep. 20, 1996, in brief, disclosed a gas, and especially air, bath foam tester having an insulated cabinet with a temperature-regulatable volume contained therein; a heater capable of heating a gas for the volume; a feature to circulate heated gas in the volume; an access system such that sample container(s), each capable of holding a liquid sample, is(are) insertable into the volume so that the same can be heated therein; and a feature to observe any sample(s) in the sample container(s) such that observation can be conducted from outside the cabinet--and further wherein cooling can be provided by water or other liquid and/or by insert of a cooling device, for example, an insert in place of a foam tester sample "carousel" or an insert which may penetrate the side of the cabinet. A foam testing protocol was disclosed in which the heating mode of the device was alternated with a cooling mode so that samples could be tested more quickly in the same device. As well, a special pourable sample container was provided thereby.
As significant as that invention is to the art--and it has commercial ramifications as showed by Savant, Inc., Lubrication Technology, "Foam Testing Now Available," September 1996, it is not without drawbacks. Chief among these is that, according to an ever-present drive to improve efficiencies, that foam tester can take longer to cool down between tests than desired.
The following art was cited by the U.S. examiner in the first action in the aforesaid '822 application:
Smith et al., U.S. Pat. No. 2,380,679. This discloses an apparatus for testing the foaming characteristics of liquids, more particularly, an oil-submersible aerator.
Groll, Jr., et al., U.S. Pat. No. 3,027,755. This discloses an apparatus and method for determining effectiveness of defoamers in foamy systems, more particularly, in strippable foamy system, i.e., a fluid system which upon agitation results in the production of froth or foam and containing one or more components which are to be stripped or removed therefrom, e.g., a synthetic rubber lattice produced by copolymerizing unsaturated compounds such as 1,3-butadiene and styrene.
Callaghan et al., U.S. Pat. No. 4,577,491. This discloses a method for determining the stability of foam, which includes a sample pressurizing vessel connected to a sample injection chamber leading to a sample cell linked to a reference cell maintained at constant pressure.
Lehnert et al., U.S. Pat. No. 5,154,088. This discloses apparatuses and methods for incorporating blowing agents into liquids for the production of polymer foams and for measuring the volumetric expansion potential of mixtures thereof. An apparatus thereof includes a high pressure liquid storage and mixing tank.
Winstead et al., U.S. Pat. No. 5,336,866. This discloses a fabric sample treatment apparatus, which is for effecting the controlled and uniform heating of a plurality of fabric and dye liquor specimens, and which includes a heating chamber having a rotatable sample rack, a radiant heat source, multidirectional cooling air vents, temperature measurement devices for monitoring chamber and specimen temperature, and control equipment.
Loisel, U.S. Pat. No. 5,465,610. This discloses a device for the characterization of the foaming properties of a product which is at least partially soluble, which includes a transparent analysis column with a porous base to introduce a gas flow, and an automatic measuring system.
Mullen, U.S. Pat. No. 5,597,950. This discloses surfactant monitoring by foam generation, a device of which detects the formation of foam with a light beam or conductivity measurement.
Arthur H. Thomas Co., Philadelphia, Pa., 1974 Parts Catalog, page 102. This discloses glass beakers.
The following art was initially cited by the U.K. examiner in a search report dated May 22, 1997 in British patent application No. GB 9704236.0 corresponding to the aforesaid '822 application:
Lunick, U.S. Pat. No. 4,356,967. This discloses a laboratory incubator chamber system, which includes an air-tight sealed compartment for providing an incubation chamber and a sealed control compartment for housing electronic circuitry.
Selfridge et al., U.S. Pat. No. 4,572,427. This discloses a controlled atmosphere enclosure, which is an incubator having a housing defining a thermally insulated chamber with a controlled gas atmosphere. Sensing devices are in a gas recirculation path outside the incubator chamber. The gas atmosphere circulates from a chamber outlet in an upper portion of the chamber, through the recirculation path, returning to the incubator chamber through an inlet in a lower portion of the chamber. Included in the recirculation path are a recirculation blower, a filter, a carbon dioxide sensor, and a humidifier.
European patent application publication No. 0 252 738 A2. This discloses a foam meter, which includes a thermostatically controlled column open at one end with a mesh at the other end.
U.K. patent specification No. 1,186,105. This discloses a humidity cabinet, which includes a plurality of moisture-proof compartments for samples to be tested, each compartment having a door which can be opened or closed as desired, a fan in each compartment, a common drive means for the fans located outside the compartments, and a timing device controlling the operation of the fans.
U.K. patent specification No. 1 313 970. This discloses an apparatus for laboratory testing of sustained release drugs, which includes a heatable chamber, means for accurately controlling the temperature in the chamber and including a mercury bulb thermometer located within the chamber, a relay operating switch connected to a heat source for the chamber, and a rotatable wheel-shaped device located within the chamber and supporting a number of elution bottle housings.
U.K. patent application No. GB 2 157 833 A. This discloses testing oil for emulsion formation, which includes a test rig--meant to simulate engine operating conditions so as to determine the propensity of various oils to form water-in-oil emulsions in the rocker covers of the engine--in which heated oil and heated saturated air, or raw steam, are directed by delivery pipes onto an inclined test plate disposed inside a cabinet and cooled.
U.K. patent application No. GB 2 169 086 A. This discloses an apparatus for testing of fluids, especially for physical characteristics or susceptibility of process fluids, e.g., oil, to foam or form an emulsion, which includes a rotor with at least one arcuate and preferably transparent pipe segment that can transport the test fluid at various speeds during the rotation.